Electrical controls for elevators



Dec. 29, 1959 o. HAASE ETAL 2,918,987

ELECTRICAL CONTROLS FOR ELEVATORS Filed Aug. 20, 1958 2 Sheets-Sheet 1 2-50 310 1 1 20 V. y 614 v a Z T T I 2%;

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INVENTORS 0 T TO AMA s5 71 an V04 KEPT United States Patent ELECTRICAL CONTROLS FOR ELEVATORS Otto Haase, Dresden, and Erich Volkert, Erfurt, Germany, assignors to VEB Starkstrom-Anlagenbau Erfurt, Erfurt, Germany Application August 20, 1958, Serial No. 756,130

Claims priority, application Germany August 28, 1957 Claims. (Cl. 187-49) The present inventionrelates to electrical controls for high speed elevators such as in mines, andto their automatic operation.

The automatic controldevices of'the prior art for elevators operate at constantcurrent consumption during acceleration and deceleration, i.e. the electrical turning moment for starting and for slowing down is constant and independent of the load, and of the direction of travel (either lowering into the mine or raising out of the mine). The absolute or overall value of the acceleration or deceleration in these prior devices, however, depends on the arrangement of load, acceleration, and deceleration prevailing at any given moment; it is also variable and causes variation in acceleration distanceand braking distance. The accelerating distance is limited by controlling the number of revolutions and travel at constant speed is initiated thereby.

The point at which deceleration must begin varies because of the necessary length of braking distance. A sensing device adapts the deceleration path to the prevailing load conditions and initiates deceleration accordingly at an earlier or later moment. Such a sensing device and the corresponding control devices for such prior control installations are complicated and costly. Such devices increase the maintenance requirements for control and increase the cost of operation. Control devices of known design usually operate with mechanical control means which serve primarily for adjusting the speed of revolution to a predetermined value and which can be made use of for initiating the deceleration. Commonly used control devices are preferably magnetic amplifiers or rotary drum switches. 1

According to the present invention, the elevator is controlled in such a manner that distance and time of acceleration travel at constant speed and deceleration remain constant, independent of the load in each traveling cycle. Contrary to the wiring arrangements of the prior art, not the actual current is controlled during starting, but rather the acceleration or deceleration is directly controlled. Direct adjustment of the rotary speed. occurs during travel at constant speed.

According to the invention, control of the rotary speed and of the acceleration starts with the start of the elevator trip. The predetermined full speed, rate of revolution, and the predetermined value of the acceleration are set by means of the basic excitation of an amplidyne amplifier device, and the acceleration winding fully compensates basic excitation up to the point of constant acceleration, whereas in the transition area, or during the transition period, up to constant rotary speed, the rotary speed regulating winding compensates the basic excitation, and basic excitation at constant rate travel is finally entirely cancelled or compensated for by the rotary speed regulating winding, whereby excitation for the rotary speed required at any given time is supplied by the rotary speed compensating winding subject to the potential of a tach0-.

generator driven by the elevator motor.

2,918,987 Patented Dec. 29, 1959 ice The braking process is initiated directly by the control element, dependent. upon the position of; the elevator cage, and constant deceleration is achieved by setting of a predetermined value of a predetermined base excitation which is negative relative to the acceleration, while simultaneously the rotary speed control is disconnected. The acceleration winding then fully compensates basic excitation and the rotary speed compensation winding supplies the corresponding rotary speed value.

As soon as the minimum velocity is reached during deceleration, the crawling or inching speed is controlled in such a manner that the crawling speed winding becomes effective during transition to constant crawling speed and compensates the basic excitation together with the deceleration winding, whereas at constant velocity at crawling'speed, basic excitation is cancelled by the crawling speed winding and therequired rotary speed is regulated by the rotary speed comipensating winding.

Independence from the size of the load is achieved by coaction of a compounding device of known design, and a compensating device of the invention controlling It is another characteristic of the invention that use of a mechanical travel control is eliminated, its functions being assumed by a plurality of switches in the elevator shaft which coact with various exciter windings of the amplidyne amplifier and with. a combination of suitable relays.

It is therefore an object of the present invention to provide an electrical control device for elevators which will contribute to the overall acceleration or deceleration of the elevator cage during its travel being independent of load and of the acceleration or deceleration prevailing at any given moment.

It is another object of the invention to provide an electrical control device for elevators which will cause the distance of and time of acceleration, time at constant speed and time of deceleration to remain constant, independent of the load in each traveling cycle.

Other objects and many of they attendant advantages thereof will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

Fig. 1 shows a schematic wiring diagram of one embodiment of the invention;

Fig. 2 is a diagrammatic view of the elevator shaft showing the arrangement of switches; and

Fig. 3 is a schematic wiring diagram showing the relays connected to the switches of Fig. 2.

It will be understood in the drawings that wherever relays are used, the windings and other parts are usually but not always, vertically aligned. Because some relay windings of Fig. 3 operate contacts in circuits shown in Fig. 1, the co-acting parts are described by similar numerals. The preface R to any numeral in Fig. 3 is indicative of the winding of the relay. The preface CR is indicative of the contacts in the relays actuated by the windings of like numeral. Lower case sufiixes distinguish various contacts in the relays.

Each aligned relay circuit in Fig. 3 is indicated by an S followed by a numeral. The chart below each circuit should be understood as an indication of which other S circuit the particular relay winding in that circuit is intended to'affect either by opening or closing relays within that circuit.

The basic element of the control device of the invention is an amplidyne amplifierA, having nine galvanically separated excitor windings for: Basic excitation 1,

3 rotary speed control 2, crawling speed control 3, stabilizing 4, acceleration control 5, rotary speed compensation 6, killing circuit 7,

compensation 8, and compounding 9. This amplidyne A feeds the control generator G of a converter unit indicated generally as 60, and which in turn supplies the necessary direct current for the elevator motor M. A

tacho-generator TG is mounted on the shaft of elevator motor M and serves as means for transmitting a current proportional to the actual rate of revolution of motor M. The corresponding combination of relays initiates various control processes as follows:

The generator G of converter unit 60 is excited by means of the amplidyne A in such a manner that the elevator motor M raises the cage with a constant acceleration. Starting is a predetermined adjustable point, the rotary speed of motor M increases and approaches a fixed value according to a logarithmic e-function. After reaching this fixed value the rate of revolution of motor M is held constant by means of a control circuit and, starting at the point of deceleration, the motor speed of motor M approaches, with constant deceleration, a crawling speed. As soon as a certain minimum speed of revolution of motor M is reached the speed thereof then further decreases according to a logarithmic e-function to the crawling speed. This crawling speed is then held constant until the cage reaches the mouth of the elevator shaft and mechanical brakes have been applied.

In more detail, the control and regulating processes are described as follows:

As shown in Fig. 1, windings 6 and 9 provide excitation for amplidyne A, which, acting through the generator G of converter 60, results in a voltage and flow of current which the motor M requires for the prevailing rotary speed. Winding 6, therefore, is connected, as shown, to the tacho-generator TG which is coupled with the motor M and the output current I of winding 6 is proportional to the rotary speed of motor M, and therefore to the electromotive force of the motor. Winding 9 is connected to a shunt R arranged in the circuit converter 60, and its current 1,, is proportional to the armature current I and thus to the voltage drop in the armature circuit. Both windings 6 and 9 remain effective during the entire travel cycle, without being reversed. To the effect of these is added the efiect of the compensating winding 8 which cancels out the influence of load during temporary changes of the load current, and thus, together with winding 9 causes the acceleration, deceleration and velocities to be uniform at uniform loads.

Upon starting, base excitation winding 1 is switched on and acts in the same direction as winding 6. The motor M starts up. Winding receives a current value I through a differential transformer 51, which may be connected across the potential of tacho-generator TG or across that of control generator G (as shown by dotted lines in Fig. 1), and through amplifier V, 52, the current value I being proportional to the acceleration and acting against winding 1. When the acceleration is too small, then a differential amount of current occurs between winding 1 and winding 5, which increases total excitation, i.e. acceleration increases. If the acceleration is too great, the exciting difference between winding 1 and winding 5 reduces total excitation and the acceleration is reduced. In this manner the acceleration is held constant. At the predetermined value of acceleration, winding 5 cancels the efiect of winding 1. When the basic exciter winding 1 is switched on, winding 2 is simultaneously connected to the voltage across the tachogenerator TG. It acts counter to winding 1 when the tacho-generator voltage becomes greater than the voltage for which the potentiometer P fis set. As long as the tacho voltage is smaller than U the rectifiers 53, 54

prevent flow of current in the opposite direction. When W is effective W and W together balance W As I increases, I and thus the acceleration, decreases. When the terminal speed is reached, the acceleration has become zero, and W accordingly regulates the rotary speed of motor M corresponding to W If the machine is decelerated, winding 1 is reversed and winding 2 is disconnected. Winding 1 reduces the rotary speed of motor M and is then cancelled by the exciter winding 5 which has also been reversed after deceleration has been initiated. The rotary speed of motor M decreases at constant deceleration. At the beginning of the deceleration, winding 3 was connected across the tacho potential U Winding 3 operates when tacho potential U becomes smaller than the voltage U set on potentiometer P As long as U is greater than U a rectifier prevents a flow of current. As soon as the voltage U drops below U deceleration decreases, and the rotary speed of motor M passes into crawling speed.

The adjustment of the individual operating parameters or values such as acceleration, deceleration, speed, etc., may be performed as follows:

The predetermined value of acceleration or deceleration can be adjusted, first by changing the basic exciter currents I by means of resistor R and potentiometer P whereby the terminal rotary speed of motor M also is changed. If it is desired to change only the acceleration or deceleration, the resistor R and thus the input current I of the differential transformer 51 has to be adjusted. Terminal rotary speed is adjustable first, as above mentioned, by adjustment of the basic exciting current I whereby acceleration and deceleration are also altered, but also by variation of potential U in potentiometer P In this case, the rotary speed also changes, which constitutes the speed to which acceleration is continued. If the terminal speed is to be changed without changing acceleration and point of initiation thereof, resistor R must be regulated. Crawling speed changes with the variation of the rotary speed up to which deceleration remains constant, by means of adjustment of voltage U at potentiometer P Crawling speed furthermore changes with the basic excitation I of winding 1. Independent of I and U it may also be adjusted by means of R A relay combination, which is actuated by the switches located in the elevator shaft initiates the individual control processes. 7

The mode of operation of the invention will be evident from the following example:

Let it be assumed that north and south elevator cages are in the position indicated in Fig. 2. Then, the terminal arresting switch A and deceleration switch V of Fig. l are closed, and the relays R10, R11 and R12 are energized, i.e. the desired value for the acceleration of the north cage, which is to be raised, is set. However, this value has not yet been applied to the basic exciter windingl, since relay switch CR13 is still open. Relay R12 causes a residual voltage of control generator G at rest to be applied to the exciter winding 7 so that by the residual magnetism or remanence of control generator G and of the amplidyne A are eliminated. By the ON command, relays R13 and R1311 are energized, and at the same time relay R12 is deenergized. The machine thus starts at the set acceleration and automatically reaches its constant terminal velocity. When the north cage reaches switch V relay 11 is deenergized and relay 14 is energized, whereby the predetermined value for deceleration is set. At the same time, rotary speed control is disconnected by means of relay R15, and the relay R16 is switched on, thus setting crawling speed with the proper polarity. As soon as the north cage finally reaches switch A the On-relay R13 and R13a is deenergized, and the machine comes to a standstill. At the same time the killing circuit 7 becomes effective and acceleration is set for the downward movement of the north cage. The opposite cycle can then start. The switches 6 and 6;, shown in Fig. 2, serve as safety speed limit switches or governors. If the cage at this point has attained a speed which is above a certain permissible value, the safety brake is released by means of a centrifugal switch or similar device.

Obviously, many modifications and variations of th present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than specifically described.

We claim:

1. An electrical automatic control device for an elevator to maintain constant and independent of variations in the elevator load, the values of distance of and time of acceleration, of travel at constant speed and of deceleration; comprising an elevator motor, direct current generator means for driving said motor, amplidyne amplifier means for feeding current to said generator, tachogenerator means operatively connected to said elevator motor for generating a current proportional to the rotary speed of said motor, said amplidyne amplifier means being provided with a plurality of exciter windings, including a basic excitation winding, a rotary speed regulating winding, an acceleration winding, and a rotary speed compensating winding connected across the voltage of said tacho-generator, whereby at the beginning of each travel cycle of said elevator simultaneous control of the rotational speed and acceleration of said elevator motor are achieved through said basic excitation winding of said amplidyne amplifier means, said acceleration winding fully compensating said basic excitation winding up to the point of constant acceleration of said motor, whereas in the region of transition from acceleration to constant rotary speed of said motor said speed regulating winding compensates the current from said basic excitation winding, and during subsequent rotation of said motor at constant speed said rotary speed regulating winding cancels out the current from said basic excitation winding, and said rotary speed compensating winding then supplying excitation at any given instant to said amplidyne amplifier means.

2.. A device according to claim 1, said elevator having a cage and including braking means for stopping the cage of said elevator, switch means for initiating operation of said braking means, said switch means being located in the shaft of said elevator and actuatable by the position of said cage, means for setting a predetermined value of basic excitation current in said basic excitation winding so that said basic excitation current is negative relative to the current from said acceleration winding, means for simultaneously disconnecting said rotary speed regulating winding while said acceleration winding fully compensates said basic excitation winding and said rotary speed compensating winding furnishes an exciting current to said amplidyne amplifier corresponding to the rotary speed value of said tacho-generator.

3. A device according to claim 2, including means for controlling said motor to rotate at a predetermined crawling rotary speed, comprising a crawling speed excitor winding and a deceleration exciter winding for said amplidyne amplifier, switch and relay means for actuating said crawling speed winding to become effective in a predetermined transition range of speed of said motor as the speed of said motor approaches said crawling speed, within said transition range said crawling speed winding and said deceleration winding together compensating said basic excitation winding, and during travel of said elevator cage at constant crawling speed said basic excitation winding is compensated by said crawling speed winding, and said rotary speed compensating winding furnishes an exciting current to said amplidyne amplifier to regulate the rotary speed of said elevator motor.

4. A device according to claim 3, including dt compensation exciter winding for said amplidyne amplifier to cancel out the influence of load during temporary change of load current to said elevator motor.

5. A device according to claim 4 including non-mechanical elevator travel control means comprising a plurality of switches located in the shaft of said elevator and operatively connected with said windings of said amplidyne amplifier, and a combination of relays connected to said switches in said elevator shaft for elfectuating the control of said windings and thus of said elevator travel.

References Cited in the file of this patent UNITED STATES PATENTS 2,742,979 Santini et a1. Apr. 24, 1956 2,746,566 Thurston May 22, 1956 

